2006 Fiscal Year Final Research Report Summary
Exploration of photonic electronic magnetic and their mutual functionalities in non-equilibrium and transparent oxide thin films accelerated by parallel epitaxy
| Project/Area Number |
14GS0204
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| Research Category |
Grant-in-Aid for Creative Scientific Research
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| Allocation Type | Single-year Grants |
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| Research Institution | Tohoku University |
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Principal Investigator |
KAWASAKI Masashi Tohoku University, Institute for Materials Research, Professor (90211862)
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| Co-Investigator(Kenkyū-buntansha) |
KAWAZOE Yoshiyuki Tohoku University, Institute for Materials Research, Professor (30091672)
FUKUMURA Tomoteru Tohoku University, Institute for Materials Research, Lecturer (90333880)
OHTOMO Akira Tohoku University, Institute for Materials Research, Research Associate (10344722)
MATSUKURA Fumihiro Tohoku University, Research Institute of Electrical Communication, Assistant Professor (50261574)
OHTANI Keita Tohoku University, Research Institute of Electrical Communication, Research Associate (40333893)
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| Project Period (FY) |
2002 – 2006
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| Keywords | Crystals Engineerng / Wide band gap Semiconductor / Oxide Semiconductors / Transistors / Spintronics / Ceramics / Optical Properties / Combinatorial |
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| Research Abstract |
After the discovery of high Tc superconductors, the research on epitaxial oxide thin films has been rapidly advanced to extend its research area to versatile functionalities such as ferroelectric, magnetic, and photonic ones. Atomic scale control of crystal growth process and heterostructures explore oxide electronics, among which oxide semiconductors play important role to realize applications that cannot be achieved by conventional semiconductors. In this research program, transparent semiconductors such as ZnO and TiO_2, are examined to donate novel photonic, electronic and magnetic functionalities through efficient parallel synthesis method. Such prototypical devices have been demonstrated as ZnO ultraviolet light emitting diodes, high mobility ZnO invisible transistors, magnetic tunnel junctions of (TiCo)_2. The followings are examples of the output. Photonic Functionality
1. Temperature gradient method was developed as one of the parallel epitaxy method to optimize the growth conditions for making world-best intrinsic ZnO.
2. P-type ZnO was produced for the first time by developing repeated temperature modulation technique to facilitate the incorporation and activation of nitrogen as acceptors.
3. Ultraviolet LED was demonstrated in ZnO pn-junctions. Electronic Functionality
4. Polycrystalline channel ZnO thin film transistors were formulated by a simulator and limiting factors of device performance were clarified.
5. A field effect mobility of 200cm2Ns was achieved in single crystalline ZnO TFT.
6. Quantum Hall effect was observed in oxide for the first time. Magnetic Functionality
7. Spin polarized nature of charge carriers in TiO_2: Co was confirmed by magneto-optic and anomalous Hall effects.
8. Magnetic tunnel junctions of TiO_2: Co was demonstrated as a first example of spin injection device of wide bandgap magnetic semiconductors.
9. Electronic structure of TiO_2: Co was studied by first principle calculation.
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